The present invention concerns a method for holographic registration, processing and reconstruction of waves by means of an optical system. The invention can also be used for the reconstruction of information with one type of wave when the hologram registration is done with another type of wave.
Production of holograms by transformation of waves by means of optical systems is known previously in various connections, for example, fourier-transforming the object wave, imaging the object and the optical scaling of holograms. The present invention represents a new holographic process which is characterized in the generation of an unrecorded hologram, herein denoted virtual hologram, which satisfies optical requirements and which corresponds to the modulation of a reference wave, herein denoted virtual reference wave, with the object wave for a particular object, herein denoted real object, said virtual hologram being in the form of the image of a recorded hologram, herein denoted real hologram, which satisfies technological requirements, and which corresponds to the modulation of the transformed virtual reference wave, herein denoted real reference wave, with the transformed object wave, corresponding to a transformed object, herein denoted virtual object, and in the transformation of the real hologram by means of the optical system and a reconstruction wave, whereby the virtual hologram is generated and the real object is reconstructed therefrom. Hereafter this method will be denoted "Virtual Holography".
It should be noted that the terms "virtual" and "real" are used here in another context than their usual meanings in optics.
The said optical system is meant to include systems that transform other waves than light waves. In analog holography according to the invention, the optical system consists of lenses and other possible optical elements while the generation of a digital hologram requires the use of the corresponding formulas for the optical system, which are known from optics. During reconstruction according to the invention, a physical optical system is used in both cases, or reconstruction is simulated with a computer and a graphical display unit.
As known, analog holography, also called classical holography, and digital holography, also called computer-generated holography, have the basic principle in common that the interference pattern of an object wave and a reference wave is registered as a hologram, and, thereafter, the object wave is reconstructed by illuminating the hologram with a reconstruction wave, which can be the same as the previous reference wave. The present invention concerns both analog and digital holography.
As is known in digital holography, the registration of the hologram often involves difficulties, partially because the hologram points have a finite area. This invention makes it possible that the holographic process is adapted to the available technology, rather than the technology, as hitherto, is adapted to the holographic process in order to satisfy the requirements of the physical waves used.